Unwell children and their families have been exposed to listeria bacteria at Queensland Children's Hospital in Brisbane.
There are concerns patients and their relatives could have eaten listeria-infected ham in sandwiches and salads.
The hospital released a statement saying it had been served between May 10 and 20.
While there have been no reports of listeria-related illnesses, health authorities warn symptoms, including vomiting and diarrhoea, could take weeks to show in people exposed to the bacteria.
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